DD261793A5 - METHOD FOR POLYMERIZING ALPHA MONOOLEFINS IN A CONTINUOUS GAS PHASE PROCESS - Google Patents

Abstract

The invention relates to a process for the polymerization of alpha-monoolefins in a continuous gas-phase process. In the improved process for the polymerization of alpha monoolefins in a continuous gas phase process in a fluidized bed using a catalyst system consisting of (a) a solid titanium containing procatalyst, (b) an organoaluminum compound activator and (c) a selectivity control agent consists Dialkylaluminiumhalogenid invention continuously added during the polymerization and the polymerization at a temperature of 0.1 to 5.0C above the dew point of the recycle gas in the reactor out.

Description

Characteristic of the known state of the art

U.S. Patent 4,414,132 to Goodall et al. teaches the use of highly active, stereospecific catalysts for the polymerization of olefins.

It is known from US-PS 4,065,609 Willmore that the polymerization of olefins in the gas phase, which is carried out in a moving bed at a temperature of 0.1 ° C to 5 ⁰ C above the dew point of the reactants, the Increased stereospecificity and the yield of olefin.

It is also known from EP-PS No. 0141461 that the performance of Goodall's catalyst can be increased by pretreating the catalyst with dialkylaluminum chloride. However, the catalyst pretreated in this way is so highly active that special treatment techniques are necessary to introduce it into the polymerization reactor. In addition, it is noted in this specification that if the catalyst has not been pretreated with dialkylaluminum chloride prior to entering the polymerization reactor, no increased yield is achieved.

Independently of this, experiments have confirmed that little or no improvement is achieved when dialkylaluminum chloride is added to the Goodall catalyst in the polymerization reactor under the usual polymerization conditions.

Object of the invention

The object of the invention is to provide an improved process for the polymerization of alpha monoolefins in a continuous gas phase process, with which highly stereospecific olefin polymers can be obtained in higher yield.

Explanation of the essence of the invention

The invention has for its object to use dialkylaluminum chloride to increase performance and use in the right way.

Surprisingly, it has been found that an unexpected increase in the activity of the catalyst can be achieved when the dialkylaluminum chloride is added to the reactor near the temperature of the dew point of the reactants.

This increase in activity is well above what one might expect when working only close to the dew point.

According to the present invention, highly stereospecific olefin polymers can be obtained with increased yield in a continuous gas phase polymerization process in a fluidized bed reactor of alpha-monoolefins by using a catalyst system consisting of

(a) a solid, titanium-containing procatalyst,

(B) an organoaluminum compound as activator and

(c) a selectivity controlling reagent

is used, dialkylaluminum halide is continuously input into the reactor during polymerization and the polymerization at a temperature of 0.1 to 5.0 ⁰ C is conducted above the dew point of Monomergasgemisches in the reactor.

According to the present invention, there is provided a method for improving the performance of catalysts in a continuous gas phase fluidized bed process for the polymerization of olefins. In particular, the performance of the catalyst is enhanced by adding dialkylaluminum halide to the polymerization reactor in addition to a procatalyst, an activator compound, and a selectivity control reagent, and operating the reactor at a temperature slightly above the dew point of the monomer gas mixture in the reactor. It can be achieved that the temperature of the dew point and the reaction temperature are close to each other, d. H. within a range of 5 ° C by raising the temperature of the dew point of the monomer mixture or lowering the reaction temperature.

Preferably, this is achieved by raising the temperature of the dew point to a value within a range of 5 ° C to the polymerization temperature. The polymerization is usually carried out at a temperature between 5O ⁰ C and 80 ⁰ C, preferably between 60 ⁰ C and 70 ⁰ C and most preferably performed between 60 ⁰ C and 65 ⁰ C. The prior art discloses a number of methods for increasing the dew point. These include z. For example, enter the following:

(a) increasing the partial pressure of the monomers, i. the partial pressure of propylene, and / or

(b) dilution of the reaction mixture with an inert gas.

If a dilution gas is used to increase the dew point of the monomer gas mixture, it should be used in an amount sufficient to raise the dew point to a value of 0.01 to 5 ° C below the reaction temperature. The amount of dilution gas depends on the nature of this gas and may range from 1 to 30, and preferably from 3 to 20, mol% of the reaction mixture.

By the term "gas for dilution" is meant a gas which does not react under the conditions in the polymerization reactor, ie it does not decompose and / or with the polymerizable monomer and the components of the catalyst combination under the polymerization conditions used in the reactor. Examples of such gases which are suitable for dilution are propane, isopentane and the like Preferred diluent gases used to increase the dew point are the relatively high molecular weight inert gases such as isopentane and propane Inert gases such as nitrogen and hydrogen have little influence on the dew point of the entire gas mixture.

However, the preferred method of increasing the dew point of the monomer gas mixture is to increase the molar concentration of the reactive monomer in the reactor and thereby increase the partial pressure of the gas mixture. Increasing the partial pressure has the desired effect of increasing the dew point of the monomer gas mixture.

The process according to the invention can be carried out with alpha-monoolefins having 2 to 8 carbon atoms, although propylene and butylene are preferred and propylene is particularly preferred. With the aid of the process according to the invention, it is likewise possible to copolymerize α-monoolefins.

Typical reactor compositions consist of 65-87% alpha monoolefin, 1-2% hydrogen and the remaining percentages from other cycle gases, e.g. As nitrogen, propane and isopentane.

The catalyst compositions that can be used in the process of this invention are described in U.S. Patent 4,414,132 to Goodall et al. described; this description is incorporated herein by reference. These compositions are a solid, titanium-containing procatalyst in combination with an organoaluminum activator compound and a selectivity controlling reagent.

The solid, titanium-containing procatalyst is obtained by using a magnesium compound of the formula MgR ₁ R ₂₁ WOrJn R ₁ an alkoxide or aryloxide group and R ₂ an alkoxide or aryloxide group or halogen, with a halide of the tetravalent titanium in the presence of a halohydrocarbon and an electron donor is halogenated in the liquid phase and subsequently this halogenated product is brought into contact with a tetravalent titanium compound. Since electron-donating compounds are used both in the preparation of the procatalyst and as the selectivity-controlling reagents, and since various electron-donating compounds can be used for both purposes, we refer to the electron-donating compound used in the preparation of the procatalyst the "electron donor" and in the other case to the selectivity controlling reagent.

Examples of halogen-containing magnesium compounds which can be used as starting materials for the halogenation reaction used in the preparation of the procatalyst are alkoxy and aryloxymagnesium halides, e.g. Isobutoxymagnesium chloride, ethoxymagnesium bromide, phenoxymagnesium iodide, cumyloxymagnesium bromide and naphthenoxymagnesium chloride.

Preferred magnesium compounds to be halogenated are selected from magnesium dialkoxides and magnesium diaryloxides. In these compounds, the alkoxide groups are best between 1 and 8 carbon atoms, and preferably between 2 and 8 carbon atoms. Examples of these preferred compounds are magnesium diisopropoxide, magnesium diethoxide, magnesium dibutoxide, magnesium diphenoxide, magnesium dinaphthene oxide and magnesium ethoxide isobutoxide. Particularly preferred is magnesium diethoxide.

In halogenation with a halide of tetravalent titanium, the magnesium compounds are preferably reacted such that magnesium halides are prepared in which the atomic ratio of halogen to magnesium is at least 1: 2. Better results are obtained when the halogenation is more complete, i. H. when producing magnesium halides in which the atomic ratio of halogen to magnesium is at least 1.5: 1. The most preferred reactions are those which result in fully halogenated reaction products, i. H. to magnesium dihalides. Such halogenation reactions are best carried out by employing a magnesium to titanium compound molar ratio of from 0.005: 1 to 2.0: 1, preferably from 0.01: 1 to 1: 1. These halogenation reactions are additionally carried out in the presence of a halohydrocarbon and an electron donor. An inert halohydrocarbon as diluent or solvent may also be present. Of course, when an inert diluent or solvent is used, it is not intended to use this as a complete substitute for the halohydrocarbon, since it is essential that the halogenation reaction occur in the presence of a halohydrocarbon.

Suitable halides of tetravalent titanium include the aryloxy or alkoxy di- and trihalogenide, z. Dihexanoxytitanium dichloride, diethoxytitanium dibromide, isopropoxytitanium triiodide and phenoxytitanium trichloride. Titanium tetrahalides are preferred, and titanium tetrachloride is the most preferred.

Suitable halogenated hydrocarbons include compounds containing a single halogen atom in the molecule, eg, butyl chloride or amyl chloride, as well as compounds containing more than one halogen atom in the molecule. Preferred aliphatic halogenated hydrocarbons are halogen-substituted hydrocarbons having 1 to 12, in particular having less than 9 carbon atoms in the molecule and at least two halogen atoms, for. For example, dibromoethane, trichloromethane, 1,2-dichloroethane, dichlorobutane, 1,1,2-trichloroethane, trichlorocyclohexane, Dichloridfluorethan, Trichlorpropa ^ trichlorofluorooctane, Dibromdifluordecan, hexachloroethane, Tetrachlorisooctan. Preferred aliphatic halohydrocarbons are carbon tetrachloride and 1,1,2-trichloroethane. Furthermore, aromatic halohydrocarbons can be used, for. Chlorobenzene, bromobenzene, dichlorobenzene, dichlorodibromobenzene, naphthyl chloride, chlorotoluene, dichlorotoluene, etc .; preferred aromatic halogenated hydrocarbons are chlorobenzene and dichlorobenzene.

The halogenation normally proceeds to the formation of a solid reaction product which can be separated from the liquid reaction medium by filtration, decantation or another suitable method and which is subsequently treated with an inert hydrocarbon as diluent, e.g. Η-hexane, isooctane, toluene, to remove unreacted materials, including physically absorbed halocarbons. After halogenation, the product is treated with a tetravalent titanium halide, e.g. With a dialkoxytitanium dihalide, alkoxytitanium trihalide, phenoxytitanium trihalide or titanium tetrahalide, for a second time. The most preferred titanium compounds are titanium tetrahalides, and especially titanium tetrachloride. By this treatment, the content of tetravalent titanium in the solid catalyst component is increased. This increase should preferably be sufficient to set in the solid catalyst component a final atomic ratio of tetravalent titanium to magnesium of from 0.005 to 3, especially from 0.02 to 1.0. For this purpose, the tetravalent titanium chloride is best contacted at a temperature between 60 ° C and 136 ° C within 0.1 to 6 hours, optionally in the presence of an inert hydrocarbon diluent. Particularly preferred temperatures on contact of the reactants are in the range of 70 ° C to 120 ⁰ C and the most preferred reaction times are between 0.5 and 3.5 hours. This reaction can take place in the form of several successive contacts of the solid with separated amounts of TiCl ₄ .

After reacting with the tetravalent titanium chloride, the procatalyst is conveniently separated from the liquid reaction medium and washed to remove unreacted titanium compounds. The titanium content of the final, washed procatalyst is best between about 1.5 to 3.6 weight percent or up to about 4.5 weight percent.

The preferred halogen atom possibly contained in the magnesium compound to be halogenated and contained in the titanium compound serving as a halogenating agent present in the tetravalent titanium halide with which the halogenated product is compounded is chlorine.

Suitable compounds which can serve as electron donors in the preparation of the procatalyst are ethers, esters, ketones, phenols, amines, amides, imines, nitriles, phosphines, phosphites, stibines, arsines, phosphoramides and alcoholates. Examples of suitable compounds are those which are mentioned in US-PS 4,136,243 or in the corresponding GB-PS 1,486,194 and in GB-PS 1,554,340 or the corresponding DE-OS 27 29126. Preferred compounds are esters and diamines, especially esters of aromatic carboxylic acids, e.g. Ethyl benzoate, methyl p-methoxybenzoate, methyl p-ethoxybenzoate, ethyl acrylate, methyl methacrylate, ethyl acetate, dimethyl carbonate, dimethyl adipate, isobutyl fumarate, isopropyl maleate, ethyl p-chlorobenzoate, hexyl p-aminobenzoate, isopropyl naphthyl, n-amyl, cyclohexanoic ethyl ester, propyl pivalate, Ν, Ν, Ν ', Ν'-tetramethylethylenediamine, 1,2,4-trimethylpiperazine, 2,3,4,5-tetraethylpiperidine and similar compounds. The preferred electron donors used in the preparation of the procatalyst are ethyl benzoate and methyl p-toluate.

The proportions of electron donors present in the preparation of the procatalyst, calculated as moles per mole of magnesium, are best in the range of 0.01 to 10, e.g. Between 0.05 and 10, preferably between 0.1 and 5.0 and most preferably between 0.01 and 1.0.

The compound used as the selectivity controlling agent may be the same as or different from the electron donor compound used to prepare the procatalyst. The preferred compounds for controlling selectivity are ethyl p-anisate and ethyl p-ethoxybenzoate.

The organoaluminum compound to be used as the activator is most preferably a trialkylaluminum compound of the formula R ₃ Al, wherein R _{2 has} up to 6 carbon atoms, ζ. Triethylaluminum, tri-n-propylaluminum, triisobutylaluminum, triisopropylaluminum and dibutyl-n-amylaluminum.

In a preferred embodiment, the procatalyst of the process is a solid catalyst of MgCl ₂ having precipitated TiCl ₄ containing an internal electron donor, such as ethyl benzoate, in which the activator is triethylaluminum and the selectivity control agent is ethyl p-ethoxybenzoate.

The dialkylaluminum halide added to the reaction system in addition to the procatalyst, the trialkylaluminum activator and the selectivity control agent can be represented by the formula R ₂ AIX, where R is an alkyl radical of 1 to 8 carbon atoms and X is a halogen, preferably Chlorine, represent. The preferred dialkylaluminum halide is diethylaluminum chloride.

The polymerization reaction is carried out so that a stream of one or more olefin monomers, e.g. Propylene, in the gas phase and substantially in the absence of catalyst poisons such as moisture, oxygen, carbon monoxide, carbon dioxide and acetylene is continuously contacted with a catalytically effective amount of a catalyst composition described above, while also continuously dialkylaluminum halide during the Polymerization is introduced into the reactor and the polymerization is carried out at a temperature of 0.1 to 5, O ⁰ C above the dew point of the monomer gas mixture in the reactor.

The attached drawing shows a fluidized bed reactor system which can be used for the polymerization of olefins according to the process of the invention. With reference to this drawing, the reactor 10 consists of a reaction zone 12 and a speed reduction zone 14.

The reaction zone 12 consists of a bed of growing polymer particles, formed polymer particles and a small amount of catalyst particles, as fluidized by the continuous stream of polymerizable and modifying gaseous components in the form of a makeup gas stream and a recycle stream through the reaction zone. To obtain a constantly intact fluidized bed, the rate of gas flow at the surface through the fluidized bed must exceed the lowest limit of the flow rate required for fluidization, and is preferably 0.2ft / s (6.08cm / s) above this minimum flow rate. Typically, gas velocity at the surface does not exceed 5.0 feet per second (152.4 cm / s), and more preferably not 2.5 feet per second (76.1 cm / s), which is sufficient. It is essential that the fluidized bed constantly contain particles so that the particulate catalyst is entrapped and distributed throughout the reaction zone. From the beginning of the reaction, the reaction zone is normally loaded with a base of particulate polymer particles before the gas stream is passed. These particles may be identical in nature to or different from the polymer particles formed. Finally, a fluidized bed of the desired polymer particles replaces the bed used at the beginning of the reaction. The flow of the bed is achieved by a high rate of monomer gas flow to and through the bed, the velocity of this recirculated gas stream being on the order of about 50 times the rate of make-up gas flow. The fluidized bed has the general appearance of a dense mass of moving particles, possibly in free, circling flow, created by the percolation of the gas through the bed. The pressure drop through the fluidized bed is equal to or slightly greater than the mass of the fluidized bed divided by the cross-sectional area. He is thus dependent on the geometry of the reactor.

The make-up gas, which generally consists of the monomer, nitrogen and hydrogen but may also contain isopentane, propane or other diluent gas, is introduced into the fluidized bed at such a rate as to maintain a steady state gas composition. The composition of the make-up gas is determined by a gas analyzer 16 disposed above the fluidized bed. The gas analyzer 16 determines the composition of the gas being circulated and the composition of the make-up gas is adjusted to maintain a substantially steady state in gas composition within the reaction zone 12.

In order to achieve complete flow, the recycled gas and, if desired, a portion of the make-up gas is returned to the reactor 10 at the base via line 18 below the fluidized bed. Above this return point, a distribution plate 20 is provided to assist the flow of the bed. The portion of the monomer gas stream that does not react in the fluidized bed forms the recirculated gas that is removed from the polymerization zone, preferably by passing it into a velocity reduction zone 14 above the fluidized bed where entrained particles have the opportunity to enter the fluidized bed falling back. The recirculated gas is then compressed in the compressor 25 and then passed through the heat exchanger 26, in which the amount of heat generated by the reaction is removed before this gas is returned to the fluidized bed. Due to the constant removal of heat from the system, no temperature gradient appears within the upper one. Eiles of the fluidized bed exist, so that the reaction temperature is kept constant. At the bottom of the fluidized bed in a layer of about 6 to 12oz (183 to 365cm), a temperature gradient will exist between the temperature of the gas introduced and the temperature of the remainder of the fluidized bed. It has been observed in this process that the fluidized bed functions to adjust the temperature of the recirculated gas above that bottom layer of the fluidized bed zone to become equal to that of the remainder of the fluidized bed, and thus to maintain the fluidized bed substantially constant Temperature is maintained under steady state conditions. The recirculated gas is then returned to the reactor 10 at its base via line 18 and finally introduced into the fluidized bed through the distribution plate 20. The compressor 25 may also be placed below the heat exchanger 26 in the process. The distribution plate 20 plays a major role in the operation of the reactor 10. The fluidized bed contains growing and already formed polymer particles as well as catalyst particles. The distribution of the recirculated gas through the fluidized bed at a rate sufficient to ensure flow at the bottom of the fluidized bed is therefore important. The distribution plate 20 serves this purpose and may be in the form of a screen, a sintered plate, a perforated plate, a bubble plate, and the like. The elements of the plate may all be stationary, or the plate may be of a mobile type, as described in U.S. Patent No. 3,298,792.

Whatever this plate is constructed, it must disperse the recirculated gas through the particles at the bottom of the fluidized bed to maintain it in a fluid state, and it must also serve to maintain a static fluidized bed of polymer particles when the fluid Reactor 10 is not in operation.

The procatalyst used in the fluidized bed is preferably stored in a reservoir 32 under a gas atmosphere for use where the gas is to be inert to the stored material and e.g. As nitrogen or argon. From this reservoir 32, it can be fed to the fluidized bed by means of a monomer or an inert gas. The procatalyst is conveniently and preferably introduced into the reactor 10, dissolved in or diluted with an inert liquid solvent, i. in a solvent that does not react with all components of the procatalyst and all other active components of the reaction system. For this purpose, hydrocarbons such as isopentane, hexane, heptane, toluene, xylene, naphtha and mineral oil are preferred. In general, the suspension or solution of the procatalyst contains between 0.1% by weight and 75% by weight of the procatalyst, usually between 5% by weight and 40% by weight of procatalyst. If desired, less concentrated or more concentrated suspensions or solutions may be used or, alternatively, the procatalyst may be added without solvent.

Of course, if a solvent is used to add the procatalyst to the reactor, it will either immediately be vaporized in the reactor to become part of the inert gas mixture of the recycled gas or remain in the polyolefin particles. Of course, the amount of solvent should be carefully determined to minimize residuals in the final polyolefin product.

The procatalyst is fed into the fluidized bed at a rate equal to its consumption at a point 30 located above the distribution plate 20.

The organoaluminum compound used as the activator, e.g. As triethylaluminum, can also be added directly to the fluidized bed, but is preferably added to the circulated gas mixture. Preferably, the addition is in the circuit below the heat exchanger, z. In general, sufficient activator should be added so that the atomic ratio of aluminum in the activator to titanium in the procatalyst, AhTi, is in the range of 40: 1 to 100: 1, and preferably in the range of 50: 1 to 80: 1.

The organoaluminum compound used as the activator, like the procatalyst, may be introduced into the reactor 10, either dissolved in or diluted with an inert liquid solvent, or alternatively it may be added in the absence of a solvent. The same inert solvents used to add the procatalyst can be used to add the activator. In general, the suspension or solution of the activator contains between 5% by weight and 75% by weight of the activator. The rate of addition of the activator depends on the rate of addition of the procatalyst and, as stated above, is such that the molar ratio of aluminum to titanium is greater than 40. Furthermore, the ratio of activator to selectivity controlling agent helps determine the isotacticity of the final polyolefin product. The means for controlling the selectivity, for. For example, ethyl p-ethoxybenzoate or ethyl p-anisate, may also be added directly to the fluidized bed, but is preferably added to the recycle gas. The addition to the circulation line below the heat exchanger is preferred, i. H. from the manifold 28 through line 28A. The preferred ratio of selectivity controlling agent (SCA), calculated as moles per mole of organoaluminum compound used as the activator, is in the range of 0.1 to 1.0 and preferably in the range of 0.2 to 0.5.

The selectivity control agent, like the procatalyst or activator, may be added to the reactor 10 either dissolved or diluted with an inert, liquid solvent or, alternatively, it may be added in the absence of the solvent. The same inert solvents used to transport the procatalyst and the activator may be used to transport the selectivity control agent. In general, the suspension or solution of the selectivity controlling agent contains between 5% and 75% by weight of the selectivity control agent.

The dialkylaluminum halide may also be added directly to the fluidized bed, but is preferably added to the recycle gas system. Preferably, the addition to the circulation line below the heat exchanger 26, i. from dial 29 through line 29A. The dialkylaluminum halide is added at a controlled rate calculated on the basis of the rate of addition of the procatalyst so that the molar ratio of dialkylaluminum halide to titanium is 5 to 25: 1 and preferably 10 to 20: 1 is. The dialkylaluminum halide, such as the procatalyst, activator, or selectivity control agent, either dissolved in or diluted with an inert, liquid solvent or, alternatively, in the absence of a solvent, may be introduced into the reactor 10. For input of the dialkylaluminum halide, the same inert solvents as used for the other reactants can be used. In general, the suspension or solution of the dialkylaluminum halide contains between 5% and 75% by weight of the dialkylaluminum halide.

Hydrogen, which is part of the supplement g; 3 can be introduced through line 18 is used as a chain transfer agent in the polymerization reaction by the process of the present invention to control the molecular weight of the polymer without adversely affecting the stereospecificity of the catalyst composition. The ratio of hydrogen to monomer is varied between about 0 to about 0.7 mole, preferably between 0 and 0.3 mole of hydrogen per mole of monomer in the gas stream.

Other gases inert to the catalyst composition, e.g. As propane, nitrogen, can also be added via the line 18 to the gas stream.

The rate of production of the polymer in the fluidized bed is controlled by the rate of addition of the catalyst components. The performance of the fluidized bed can be increased simply by increasing the input speed of the components, and can be lowered by decreasing the input speed of the components.

As any change in the input rate of the catalyst components changes the rate of reaction heat evolution, the temperature of the recycle gas is changed up or down to compensate for changes in the rate of reaction heat evolution. This ensures the setting of a substantially constant temperature in the fluidized bed. Complete equipment of both the fluidized bed and the recycle gas cooling system with appropriate equipment is, of course, necessary for temperature changes in the fluidized bed

determine so that the operator is able to make appropriate changes in the temperature of the cycle gas.

Under given operating conditions, the fluidized bed is maintained at a substantially constant level by withdrawing a portion of the fluidized bed as a product, the removal rate being equal to the rate of formation of the particulate polymer product. Since the rate of heat generation is directly related to product formation, by measuring the temperature increase of the gas across the reactor cross section (the difference between the inlet gas temperature and the gas temperature in the reactor) the rate of particulate polymer formation becomes a constant gas flow rate certainly.

The particulate polymer product is preferably continuously withdrawn at point 34 at or near the distribution plate 20 in suspension with a portion of the gas stream. The gas is blown off before the particles settle. The gas used for the suspension may also be used, as mentioned above, to drive the product from one reactor to another. It should be noted here that the activity and stereospecificity of the catalyst compositions do not require it. Apply method for catalyst removal or polymer extraction. The total content in the polymer, ie the combined content of aluminum, chlorine and titanium, may be as low as 200 ppm, even less than 100 ppm. The particulate polymeric product is best withdrawn, preferably by the mutual operation of the time dependent valves 36 and 38 defining a separation zone 40. While the valve 38 is closed, the valve 36 is open, allowing a surge of gas and product to pass into the zone 40 between it and the valve 36, which is then closed. Valve 38 is then opened, directing the product into an external withdrawal zone. The valve 38 is then closed again to perform the following extraction operation. The fluidized bed reactor is equipped with a suitable exhaust air system to vent the fluidized bed during start up or end of operation. In this reactor, no stirring devices or devices for wall cleaning are necessary. The fluid bed reactor is operated at a pressure of up to 1000 psi (70.3 kp / cm ² ), preferably at a pressure of about 150 to 600 psi (10.5 to 42.2 kp / cm ² ), most preferably pressures of 400 to 600 psi (28.1 to 42.2 kp / cm ² ).

embodiments

The following examples and methods are given to illustrate the invention, but should not be construed as limiting. The examples serving as an illustration of the invention are indicated by numbers, while the comparative examples are indicated by letters.

definitions gram G milligram mg weight Wt .-% percent % hydrogen H ₂ millimeter ml mol mol millimoles mmol melt index MFi diethylaluminum DEAC titanium Ti reaction temperature 'Reaction Temperature of the dew point dp pounds per square inch (pounds per square inch) absolute PSIA in xylene Soluble, measure of isotacticity XS

example 1 Preparation of the procatalyst

10g magnesium turnings (412mat) were reacted with ethanol at room temperature using a mixture of 100ml ethanol, 20ml xylene, 5mg mercuric chloride (0.02mmol) and 3mg iodine (0.02mmol). The implementation took 5 hours to complete. Subsequently, the liquid phase was distilled off and the resulting solid dried under nitrogen in vacuo.

10mmol of the magnesium diethoxide thus prepared was suspended at 75-85 ° C in 15 ml of chlorobenzene. To this was added 0.48 g (3.3 mmol) of monoethyl benzoate and 15 ml (136 mmol) of titanium tetrachloride. The suspension was stirred at room temperature for 1-2 hours. The solid formed was separated from the reaction medium by filtration and decantation (component a).

This component a was reacted again with a mixture of 15 ml (136 mmol) of titanium tetrachloride and 15 ml of chlorobenzene at 75-85 ° C. and the suspension was stirred at this temperature for 2 hours. The solid was filtered off and decanted off (component b).

Component b was again reacted with a mixture of 15 ml of titanium tetrachloride and 15 ml of chlorobenzene to which 0.02 ml of benzoyl chloride was added. The mixture was again heated to 75-85 ° C and kept there for 1-2 hours, filtered and dried. The solid was then washed five times in isooctane and the procatalyst was added to mineral oil.

General working methods

Propylene was homopolymerized under various reaction conditions in a fluidized bed reactor as described and illustrated herein.

In each polymerization, a procatalyst composition as described in Example 1 was diluted with mineral oil to a 40% solution, along with triethylaluminum as a solution in isopentane or neat.

Diethylaluminium chloride, also as a solution in isopentane or neat, and ethyl p-ethoxybenzoate, also as a solution in isopentane or neat, fed into the polymerization reactor. The propylene gas used in each example was added to the reaction mixture. Nitrogen and other inert materials, when needed, were also added to the reaction mixture. Hydrogen was added to the reaction mixture as a chain transfer agent to adjust the molecular weight of the produced copolymer.

Examples 2 to 5

Examples 2 to 5, in Tables I to IV below, are examples in which both parameters of the method according to the invention are used, ie. H. the temperature of the reaction was 5 ° C or less above the dew point of the recycle gas and diethylaluminum chloride (DEAC) was added to the reactor in addition to procatalyst, organoaluminum activator and the selectivity control agent. Yield increases of 40 to 65% were achieved in each example compared to examples in which no DEAC was added and the temperatures were well above the dew point (Comparative Examples A and C) or compared to examples in which DEAC was added in which however, the temperatures were still well above the dew point (Comparative Examples D and F). Significant increases in productivity were achieved over the examples where the dew point was approached but no DEAC was added (Comparative Examples B, E, and G). The examples in Tables I and II were carried out at lower pressures and with the addition of inert diluents to raise the dew point of the recycle gas, while in the examples in Tables III and IV, no inert diluents were used to increase the dew point. Essoll states that in both cases, in which the two parameters of the process according to the invention were fulfilled, an increase in yield was achieved which was greater than that which would have been expected by working only near the dew point.

It should also be noted that a greater proportion of xylene solubles, as in Table IV over Table III, results in increased yields. _f

For each example a number of reaction conditions are given.

Table I

example Comparison A comparisons 2 MFg / 10min 3.3 1.0 3.6 xylene soluble% 3.0 2.9 3.0 Yield * kg of polymer / g of Ti 197 254 321 Percent yield increase of the catalyst - ' 29% 63% Reactor pressure (PSIA) (kp / cm ² ) 415 (29.2) 440 (30.9) 415 (29.2) Reaction temperature ( ⁰ C) 65 65 65 Dew point of the cycle gas ( ⁰ C) under 55 61 62.7 Operation near dew point No Yes Yes (Traction top) (° C) > 10 4 2.3 Addition of DEAC No No Yes (DEAC / Ti), molar 17.1 Aluminum in the activator: Ti in the procatalyst 36: 1 130: 1 61: 1 AhSCA 2.3: 1 2.4: 1 2.0: 1 Mol% of propylene 72 77. 71.5 Mole percent isopentane 0.2 0.4 4.3 Mol% inert propane - 13 -

* The yield is corrected to the same partial pressure of propylene of 330 PSIA (23.2 kp / cm ² ). Table II

example comparisons MFg / 10min 3.6 Soluble in xylene,% 3.8 Yield *, kg polymer / g Ti 294 Percent yield increase of the catalyst - Reactor pressure (PSIA) (kp / cm ² ) 440 (30.9) Reaction temperature ( ⁰ C) 62 Dew point of the cycle gas ( ⁰ C) under 52 Operation near dew point No DEAC addition No (DEAC / Ti), molar Aluminum in the activator: Titanium in the procatalyst 69: 1 AhSCA 1.8: 1 Mol% of propylene 74.5 Mole percent isopentane 0.5 Mol% inert propane -

4.0 3.6 461 56% 440 (30.9)

Yes

Yes, 26: 1

131: 1 1.7: 1 63.8 0.9 16

* The yield is corrected to the same partial propylene pressure of 330PSIA (23.2 kp / cm ² ).

Comparison D Forgot E -8- 261 793 Table III 7.9 1.8 example 3.4 3.4 4 MFg / 10min 371 460 1.4 Xylene solubles,% - 24 3.3 Yield *, kg polymer / g Ti 490-500 490-500 528 Percent yield increase of the catalyst (34.5 to 35.2) (34.5 to 35.2) 42 Reactor pressure (PSIA) (kp / cm ² ) 62-64 65 490-500 under 52 63.4 (34.5 to 35.2) Reaction temperature ( ⁰ C) No Yes 65 Dew point of the cycle gas ( ⁰ C) > 10 1.6 64 Operation near dew point Yes, 10: 1 No Yes (TReaction-TDp) (° C) 40: 1 32: 1 1 DEAC addition (DEAC / Ti), molar Yes, 10: 1 Aluminum in the activator: 1.9: 1 3.4: 1 41: 1 Titanium in the P rocatalyst 73 82 AhSCA - - 2.2: 1 Mol% of propylene - - 85 Mole percent isopentane - Mol% inert propane -

* The yield is corrected to the same partial pressure of propylene of 330 PSIA (23.2 kp / cm ² ). Table IV

example Comparison F MFg / 10min 8.0 Xylene Soluble,% 3.8 Yield *, kg polymer / g Ti 402 Percent yield increase of the catalyst - Reactor pressure (PSIA) (kp / cm ² ) 490-500 (34.5 to 35.2) Reaction temperature ( ⁰ C) 64 Dew point of the cycle gas ( ⁰ C) below 54 Operation near dew point No DEAC addition Yes (DEAC / Ti), molar 10: 1 Aluminum in the activator: Titanium in the procatalyst 40: 1 AhSCA 1.8: 1 Mol% of propylene 75.6 Mole percent isopentane - Mol% inert propane -

Comparison G 5 1.6 1.4 3.8 3.7 544 610 36 52 490-500 490-500 (34.5 to 35.2) (34.5 to 35.2) 65 65 63.6 62.6 Yes Yes 1.9 2.4 No Yes 10: 1 34.5: 1 37.9: 1 3.2: 1 2.6: 1 82.0 84.0

The yield is corrected to the same partial propylene pressure of 330 PSIA (23.2 kp / cm ² ).

Claims (11)

A process for the polymerization of alpha monoolefins in a continuous gas phase process in a fluidized bed using a catalyst system consisting of (a) a solid, titaniferous procatalyst, (b) an organoaluminum compound activator, and (c) a selectivity control agent characterized in that dialkylaluminum halide is continuously added during the polymerization and the polymerization is carried out at a temperature of 0.1 to 5.0 ° C above the dew point of the recycle gas in the reactor. 2. The method according to claim 1, characterized in that the solid, titanium-containing procatalyst has been obtained by a magnesium compound of the formula MgR ₁ R ₂ , wherein R _{1 is} an alkoxide or aryloxide group and R _{2 is} an alkoxide or aryloxide group or halogen, is halogenated with a halide of the tetravalent titanium in the presence of a halohydrocarbon and an electron donor in the liquid phase, and then this halogenated product is contacted with a halide of the tetravalent titanium and thereafter washed to remove unreacted titanium compounds and the solid product win. 3. The method according to claim 2, characterized in that the solid, titanium-containing procatalyst is a solid catalyst of MgCl ₂ with precipitated TiCl ₄ and an electron donor. 4. The method according to claim 3, characterized in that the electron donor is ethyl benzoate. 5. The method according to any one of claims 1 to 4, characterized in that the dialkylaluminum halide R _{2 is} AIX, wherein R is an alkyl group having 1 to 8 carbon atoms and X is halogen. 6. The method according to claim 5, characterized in that R _{2 is} AIX diethylaluminum chloride. 7. The method according to any one of claims 1 to 6, characterized in that the organoaluminum compound used as activator is a trialkylaluminum compound of the formula R ₃ Al, in which R 2 to 6 carbon atoms. 8. The method according to claim 7, characterized in that R ₃ AI is triethylaluminum. 9. The method according to any one of claims 1 to 8, characterized in that the means for controlling the selectivity p-ethoxybenzoic acid ethyl ester. TO. Process according to any one of Claims 1 to 8, characterized in that the selectivity control agent is p-anisic acid ethyl ester. 11. The method according to any one of claims 1 to 10, characterized in that the ratio of activator to titanium 40: 1 to 100: 1. 12. The method according to any one of claims 1 to 11, characterized in that the ratio of dialkylaluminum halide to titanium 5: 1 to 25: 1. For this 1 page drawing
Field of application of the invention The invention relates to a process for the polymerization of alpha-monoolefins in a continuous gas phase process in a fluidized bed using a catalyst system consisting of (a) a solid, titanium-containing procatalyst, (b) an organoaluminum compound as an activator and (c) a control agent the selectivity exists.